Artifact reduction method and apparatus and image processing method and apparatus

ABSTRACT

Artifact reduction method and apparatus, and image processing method and apparatus are provided. The artifact reduction apparatus includes a scaling-down unit, a buffer unit, an artifact detection unit, a scaling-up unit and a filter unit. The scaling-down unit scales down a resolution of a current original image frame to obtain a current low-resolution image frame. The artifact detection unit performs an artifact detection to the current low-resolution image frame to obtain low-resolution weights in accordance with a relation of the current low-resolution image frame and a previous low-resolution image frame provided by the buffer unit. The scaling-up unit scales up a number of the low-resolution weights to obtain a high-resolution weights. By using the high-resolution weights, the filter unit performs an image processing procedure to the current original image frame for reducing artifact of the current original image frame and obtaining an adjusted image frame.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to an image processing apparatus, and moreparticularly, to artifact reduction method and apparatus and imageprocessing method and apparatus.

Description of Related Art

Composite video systems (e.g., NTSC or PAL) transmit color informationthrough color sub-carriers superimposed on luminance signals. Generally,luminance signals and chrominance signal share frequency bands commonlyin practical uses. As a result, two types of artifacts (e.g.,cross-chroma and cross-luma) are usually found in composite videos.

When a frequency component of the luminance signal is close to afrequency of the color sub-carrier, a cross-chroma may occur to causegeneration of color noise in frames. The cross-chroma may sometimes bereferred to as bleeding or rainbow effects. Cross-luma occurs nearbyedges with highly saturated color, and acts like a series of crawlingdots (or also known as dot crawls). Cross-luma often results in colorinformation being confused with brightness information. For viewers,artifacts like cross-luma in stationary areas are quite obvious andannoying.

SUMMARY OF THE INVENTION

An artifact reduction method is disclosed according to embodiments ofthe invention, including: scaling down a resolution of a currentoriginal image frame from a first resolution to a second resolution toobtain a current low-resolution image frame, wherein the currentoriginal image frame and the current low-resolution image frame includea first plurality of pixels and a second plurality of pixels,respectively; performing an artifact detection to the currentlow-resolution image frame to obtain a plurality of low-resolutionweights, wherein the low-resolution weights are respectivelycorresponding to the second plurality of pixels of the currentlow-resolution image frame; scaling up a number of the low-resolutionweights to generate a plurality of high-resolution weights, wherein thehigh-resolution weights are respectively corresponding to the firstplurality of pixels of the current original image frame; and performinga temporal noise reduction to the current original image frame by usingthe high-resolution weights for reducing artifact of the currentoriginal image frame and obtaining an adjusted image frame.

An image processing method is disclosed according to embodiments of theinvention, including: scaling down a resolution of a current originalimage frame from a first resolution to a second resolution to obtain acurrent low-resolution image frame, wherein the current original imageframe and the current low-resolution image frame include a firstplurality of pixels and a second plurality of pixels, respectively;generating a plurality of low-resolution weights according to thecurrent low-resolution image frame, wherein the low-resolution weightsare respectively corresponding to the second plurality of pixels of thecurrent low-resolution image frame; scaling up a number of thelow-resolution weights to generate a plurality of high-resolutionweights, wherein the high-resolution weights are respectivelycorresponding to the first plurality of pixels of the current originalimage frame; and performing an image processing procedure to the currentoriginal image frame by using the high-resolution weights to obtain anadjusted image frame.

The artifact reduction apparatus is disclosed according to embodimentsof the invention, including a scaling-down unit, a buffer unit, anartifact detection unit, a scaling-up unit and a filter unit. Thescaling-down unit scales down a resolution of a current original imageframe from a first resolution to a second resolution to obtain andoutput a current low-resolution image frame, wherein the currentoriginal image frame and the current low-resolution image frame includea first plurality of pixels and a second plurality of pixels,respectively. The buffer unit is coupled to the scaling-down unit toreceive and store the current low-resolution image frame. The artifactdetection unit is coupled to the scaling-down unit and the buffer unit.The artifact detection unit performs an artifact detection to thecurrent low-resolution image frame to obtain and output a plurality oflow-resolution weights in accordance with a relation of the currentlow-resolution image frame provided by the scaling-down unit and atleast one previous low-resolution image frame provided by the bufferunit, wherein the low-resolution weights are respectively correspondingto the second plurality of pixels of the current low-resolution imageframe. The scaling-up unit is coupled to the artifact detection unit.The scaling-up unit scales up a number of the low-resolution weights toobtain and output a plurality of high-resolution weights, wherein thehigh-resolution weights are respectively corresponding to the firstplurality of pixels of the current original image frame. The filter unitis coupled to the scaling-up unit. The filter unit performs an imageprocessing procedure to the current original image frame by using thehigh-resolution weights for reducing artifact of the current originalimage frame and obtaining an adjusted image frame.

An image processing apparatus is disclosed according to embodiments ofthe invention, including a scaling-down unit, a weight generation unit,a scaling-up unit and an adjusting unit. The scaling-down unit scalesdown a resolution of a current original image frame from a firstresolution to a second resolution to obtain a current low-resolutionimage frame. The current original image frame and the currentlow-resolution image frame include a first plurality of pixels and asecond plurality of pixels, respectively. The weight generation unitgenerates a plurality of low-resolution weights according to the currentlow-resolution image frame. The low-resolution weights are respectivelycorresponding to the second plurality of pixels of the currentlow-resolution image frame. The scaling-up unit scales up a number ofthe low-resolution weights to generate a plurality of high-resolutionweights. The high-resolution weights are respectively corresponding tothe first plurality of pixels of the current original image frame. Theadjusting unit performs an image processing procedure to the currentoriginal image frame by using the high-resolution weights to obtain anadjusted image frame.

To make the above features and advantages of the disclosure morecomprehensible, several embodiments accompanied with drawings aredescribed in detail as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating circuitry of an artifactreduction apparatus according to an embodiment of the invention.

FIG. 2 is a flowchart illustrating an artifact reduction methodaccording to an embodiment of the invention.

FIG. 3 is a schematic diagram illustrating operations of the artifactdetection unit according to an embodiment of the invention.

FIG. 4 is a block diagram illustrating circuitry of an artifactreduction apparatus according to another embodiment of the invention.

FIG. 5 is a block diagram illustrating circuitry of an artifactreduction apparatus according to yet another embodiment of theinvention.

FIG. 6 is a flowchart illustrating an artifact reduction methodaccording to yet another embodiment of the invention.

FIG. 7 is a block diagram illustrating circuitry of an artifactreduction apparatus according to another embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS

The term “coupling/coupled” used in this specification (includingclaims) may refer to any direct or indirect connection means. Forexample, “a first device is coupled to a second device” should beinterpreted as “the first device is directly connected to the seconddevice” or “the first device is indirectly connected to the seconddevice through other devices or connection means.” Moreover, whereverappropriate in the drawings and embodiments, elements/components/stepswith the same reference numerals represent the same or similar parts.Elements/components/steps with the same reference numerals or names indifferent embodiments may be cross-referenced.

FIG. 1 is a block diagram illustrating circuitry of an image processingapparatus (e.g., an artifact reduction apparatus 100) according to anembodiment of the invention. The artifact reduction apparatus 100includes a scaling-down unit 110, a buffer unit 120, a weight generationunit 130, a scaling-up unit 140 and an adjusting unit 150. In thepresent embodiment, the weight generation unit 130 may include anartifact detection unit 131, and the adjusting unit 150 may include afilter unit 151. The scaling-down unit 100 and the filter unit 151receive a current original image frame. The filter unit 151 of theadjusting unit 150 may perform an image processing procedure to thecurrent original image frame for reducing artifact of the currentoriginal image frame, and obtaining and outputting an adjusted imageframe.

FIG. 2 is a flowchart illustrating an image processing method (e.g., anartifact reduction method) according to an embodiment of the invention.Referring to FIG. 1 and FIG. 2, in step S210, the scaling-down unit 110scales down a resolution of the current original image frame from afirst resolution to a second resolution to obtain a currentlow-resolution image frame to be outputted to the buffer unit 120 andthe artifact detection unit 131 of the weight generation unit 130. Forinstance, the scaling-down unit 110 may scale down the resolution of thecurrent original image frame from high-definition (HD) resolution orFull-HD resolution to standard-definition (SD) resolution (720*480i,720*480p) or other resolutions.

The buffer unit 120 is coupled to the scaling-down unit 110 and used toreceive and store the current low-resolution image frame provided by thescaling-down unit 110. The artifact detection unit 131 of the weightgeneration unit 130 is coupled to the scaling-down unit 110 and thebuffer unit 120. In step S220, the artifact detection unit 131 of theweight generation unit 130 may generate a plurality of low-resolutionweights WL for the scaling-up unit 140 according to the currentlow-resolution image frame provided by the scaling-down unit 110,wherein the low-resolution weights WL are respectively corresponding toa second plurality of pixels of the current low-resolution image frame.For instance, in step S220, the artifact detection unit 131 may performan artifact detection to the current low-resolution image frame providedby the scaling-down unit 110, so as to obtain the low-resolution weightsWL for the scaling-up unit 140. In case the current low-resolution imageframe provided by the scaling-down unit 110 includes x*y pixels, thelow-resolution weights WL may then include x*y weights. A bit depth ofthe low-resolution weights WL may be less than or equal to a bit depthof the current low-resolution image frame.

As another example, in step S220, the artifact detection unit 131 mayperform the artifact detection to the current low-resolution image frameto obtain a plurality of low-resolution weights to be outputted to thescaling-up unit 140 in accordance with a relation of the currentlow-resolution image frame provided by the scaling-down unit 110 and atleast one previous low-resolution image frame provided by the bufferunit 120. Take NTSC system as an example, the artifact detection unit131 may perform the artifact detection to the current low-resolutionimage frame to obtain and output the low-resolution weights inaccordance with a relation between the three of the currentlow-resolution image frame (e.g., a k^(th) low-resolution image frame)provided by the scaling-down unit 110, and a second previouslow-resolution image frame (e.g., a (k−2)^(th) low-resolution imageframe) and a fourth previous low-resolution image frame (e.g., a(k−4)^(th) low-resolution image frame) provided by the buffer unit 120.Take PAL system as an example, the artifact detection unit 131 mayperform the artifact detection to the current low-resolution image frameto obtain and output a plurality of low-resolution weights WL inaccordance with a relation between the three of the currentlow-resolution image frame (e.g., a k^(th) low-resolution image frame)provided by the scaling-down unit 110, and a fourth previouslow-resolution image frame (e.g., a (k−4)^(th)low-resolution imageframe) and an eighth previous low-resolution image frame (e.g., a(k−8)^(th) low-resolution image frame) provided by the buffer unit 120.

Each pixel in both the first plurality of pixels of the current originalimage frame and the second plurality of pixels of the currentlow-resolution image frame may include a brightness value and a colorvalue. In some embodiments, in step S220, for each pixel in the secondplurality of pixels of the current low-resolution image frame, theartifact detection unit 131 may respective execute following steps: (i)comparing a color or brightness value of a pixel of the currentlow-resolution image frame with a color or brightness value of the pixelof at least one previous low-resolution image frame; and (ii) based on acomparison result from step (ii), the artifact detection unit 131 maydecide whether to adjust a color or brightness weight corresponding tothe pixel in the low-resolution weights of the at least one previouslow-resolution image frame, so as to generate a color or brightnessweight corresponding to the pixel in the low-resolution weights WL ofthe current low-resolution image frame.

In some embodiments, the step (ii) may include: (a) if the comparisonresult satisfies a predetermined condition, the artifact detection unit131 may adjust the color or brightness weight corresponding to the pixelin the low-resolution weights of the at least one previouslow-resolution image frame to be served as the color or brightnessweight corresponding to the pixel in the low-resolution weights WL ofthe current low-resolution image frame, and (b) if the comparison resultdoes not satisfy the predetermined condition, the artifact detectionunit 131 may reset the color or brightness weight corresponding to thepixel in the current low-resolution image frame to an initial value(e.g., 0 or other values).

Take NTSC system as an example, FIG. 3 is a schematic diagramillustrating operations of the artifact detection unit 131 according toan embodiment of the invention. Other embodiments regarding PAL systemmay be inferred by reference with related description of FIG. 3. In acurve diagram depicted at lower portion of FIG. 3, a horizontal axisrepresents a time t, and a vertical axis represents a pixel value P.Referring to FIG. 1 and FIG. 3, the artifact detection unit 131 maycompare/analyze a relation between the three of a pixel in the currentlow-resolution image frame (e.g., a pixel P_(i,j) with coordinates i,jin a k^(th) low-resolution image frame 330) provided by the scaling-downunit 110, and the same pixel in a second previous low-resolution imageframe (e.g., the pixel P_(i,j) with coordinates i,j in a (k−2)^(th)low-resolution image frame 320) and the same pixel in a fourth previouslow-resolution image frame (e.g., the pixel P_(i,j) with coordinates i,jin a (k−4)^(th) low-resolution image frame 310) provided by the bufferunit 120. For instance, if the relation between the three of the pixelP_(i,j) in the (k−4)^(th) low-resolution image frame 310, the pixelP_(i,j) in the (k−2)^(h) low-resolution image frame 320 and the pixelP_(i,j) in the k^(th) low-resolution image frame 330 satisfies asinusoid (as shown in FIG. 3), the artifact detection unit 131 maydetermine that the comparison result satisfies the predeterminedcondition.

Assuming that the pixels P_(i,j) in the low-resolution image frames 310,320 and 330 include a brightness value Y, the artifact detection unit131 may check whether the comparison result of the brightness value Y ofthe pixels P_(i,j) in the low-resolution image frames 310, 320 and 330satisfies the predetermined condition (as shown in FIG. 3). Once thecomparison result satisfies the predetermined condition, it indicatesthat cross-luma occurs at the pixel P_(i,j) in the currentlow-resolution image frame (e.g., the k^(th) image frame 330).Therefore, when the comparison result satisfies the predeterminedcondition, the artifact detection unit 131 may perform calculation ofWLY_(i,j)=WLY′_(i,j)+inc, wherein WLY_(i,j) is a brightness weightcorresponding to the pixel P_(i,j) in the current low-resolution imageframe (the k^(th) image frame 330), WLY′_(i,j) is a brightness weightcorresponding to the pixel P_(i,j) in the previous low-resolution imageframe (e.g., the (k−2)^(th) low-resolution image frame 320), and inc isany real number greater than 0. In other embodiments, inc may be a realnumber greater than 0 and less than 1, so that the adjusted brightnessweight WLY_(i,j) may be less than or equal to 1. The brightness weightWLY_(i,j) may be used as one of the low-resolution weights WL.Otherwise, if the comparison result does not satisfy the predeterminedcondition, the artifact detection unit 131 may perform calculation ofWLY_(i,j)=ini, wherein ini is an initial value (e.g., 0 or other realnumbers).

Assuming that the pixels P_(i,j) in the low-resolution image frames 310,320 and 330 include a color value C, the artifact detection unit 131 maycheck whether the comparison result of the color value C of the pixelsP_(i,j) in the low-resolution image frames 310, 320 and 330 satisfiesthe predetermined condition (as shown in FIG. 3). Once the comparisonresult satisfies the predetermined condition, it indicates thatcross-color occurs at the pixel P_(i,j) in the current low-resolutionimage frame 330. Therefore, when the comparison result satisfies thepredetermined condition, the artifact detection unit 131 may performcalculation of WLC_(i,j)=WLC′_(i,j)+inc, wherein WLC_(i,j) is abrightness weight corresponding to the pixel P_(i,j) in the currentlow-resolution image frame, WLC′_(i,j) is a brightness weightcorresponding to the pixel P_(i,j) in the previous low-resolution imageframe (the (k−2)^(th) low-resolution image frame 320), and inc is anyreal number greater than 0. In other embodiments, inc may be a realnumber greater than 0 and less than 1, so that the adjusted color weightWLC_(i,j) may be less than or equal to 1. The color weight WLC_(i,j) maybe used as one of the low-resolution weights WL. Otherwise, if thecomparison result does not satisfy the predetermined condition, theartifact detection unit 131 may perform calculation of WLC_(i,j)=ini,wherein ini is an initial value (e.g., 0 or other real numbers).

The scaling-up unit 140 is coupled to the artifact detection unit 131.In step S230, the scaling-up unit 140 may scale up a number (quantity)of the low-resolution weights to obtain and output a plurality ofhigh-resolution weights WH. The high-resolution weights WH arerespectively corresponding to the first plurality of pixels of thecurrent original image frame. For instance, assuming that the currentoriginal image frame is of Full-HD resolution, the scaling-up unit 140may scale up the number of the low-resolution weights WL by 1920*1080 tobe served as the high-resolution weights WH. A bit depth of thehigh-resolution weights WH may be less than or equal to a bit depth ofthe current original image frame. For instance, the bit depth (or, acolor depth) of the current original image frame may be 8 bits (or 10bits or higher), and the bit depth of the high-resolution weights WH maybe 4 bits (or less). The bit depth of the high-resolution weights WH maybe decided based on actual design requirements.

The filter unit 151 of the adjusting unit 150 is coupled to thescaling-up unit 140. In step S240, the filter unit 151 of the adjustingunit 150 may perform an image processing procedure to the currentoriginal image frame by using the high-resolution weights WH forreducing artifact of the current original image frame and obtaining theadjusted image frame. For instance, the filter unit 151 may perform atemporal noise reduction (TNR) to the current original image frame byusing the high-resolution weights WH for reducing artifact of thecurrent original image frame and obtaining the adjusted image frame.

A composite-video may be demodulated for obtaining an original imagewith SD resolution. In some applications, the original image with SDresolution may be scaled up through postproduction into the currentoriginal image with HD resolution or other higher resolutions.Therefore, composite-video artifacts may be present in the currentoriginal image frame. After the scaling-down unit 110 scales down theresolution of the current original image frame to SD resolution, a phaserelationship of the current original image frame may still reserved inthe current low-resolution image frame. Therefore, the artifactdetection unit 131 may still detect whether the current low-resolutionimage frame includes artifacts, and output the low-resolution weightsWL. The scaling-up unit 140 may scale up the number of thelow-resolution weights WL to obtain a plurality of high-resolutionweights WH to be outputted to the filter unit 151. The high-resolutionweights WH are in response to the result of the artifact detectionperformed by the artifact detection unit 131 to the currentlow-resolution image frame. The filter unit 151 may reduce artifact ofthe current original frame according to the high-resolution weights WHto obtain the adjusted image frame. Because the resolution of theoriginal image frame may be scaled down for the artifact detection, acircuit area and a calculation complexity of the artifact detection unit131 may be saved, and a memory space of the buffer unit 120 may also besaved.

FIG. 4 is a block diagram illustrating circuitry of an artifactreduction apparatus 400 according to another embodiment of theinvention. The artifact reduction apparatus 400 includes a scaling-downunit 110, a buffer unit 120, an artifact detection unit 131, ascaling-up unit 140 and a filter unit 450. The scaling-down unit 110,the buffer unit 120, the artifact detection unit 131 and the scaling-upunit 140 as shown in FIG. 4 may be inferred by reference with relateddescription of FIG. 1. The scaling-down unit 100 and the filter unit 450receive a current original image frame. The filter unit 450 may performan image processing procedure to the current original image frame forreducing artifact of the current original image frame, and obtaining andoutputting the adjusted image frame.

In the embodiment depicted in FIG. 4, the filter unit 450 includes aframe memory 451 and a temporal noise reduction (TNR) circuit 452. Theframe memory 451 may temporally store the adjusted image frame andprovide a previous adjusted image frame to the temporal noise reductioncircuit 452. The temporal noise reduction circuit 452 is coupled to theframe memory 451 and the scaling-up unit 140. The temporal noisereduction circuit 452 may perform a temporal noise reduction to thecurrent original image frame according to the high-resolution weights WHprovided by the scaling-up unit 140 and the previous adjusted imageframe provided by the frame memory 451 for reducing artifact of thecurrent original image frame and obtaining the adjusted image frame.

For instance, for each pixel in the pixels of the current original imageframe, the temporal noise reduction circuit 452 of the filter unit 450may respectively execute following steps: calculating an equation beingOut(f)=In(f)*(1−a)+In(f−1)*a. Therein, Out(f) indicates a color orbrightness value of a pixel of the adjusted image frame (e.g., the pixelP_(i,j) with coordinates i,j in a f^(th) adjusted image frame), In(f)indicates a color or brightness value of the pixel of the currentoriginal image frame (e.g., the pixel P_(i,j) with coordinates i,j in af^(th) original image frame), In(f−1) indicates a color or brightnessvalue of the pixel of the previous adjusted image frame (e.g., the pixelP_(i,j) with coordinates i,j in a (f−1)^(th) adjusted image frame)provided by the frame memory 451, and a indicates a color or brightnessweight corresponding to the pixel in the high-resolution weights WH.

FIG. 5 is a block diagram illustrating circuitry of an artifactreduction apparatus 500 according to another embodiment of theinvention. The artifact reduction apparatus 500 includes a buffer unit520, a weight generation unit 530, and an adjusting unit 550. In thepresent embodiment, the weight generation unit 530 may include anartifact detection unit 531, and the adjusting unit 550 may include afilter unit 551. The buffer unit 520, the artifact detection unit 531and the filter unit 551 as shown in FIG. 5 may be inferred by referencewith related description of the buffer unit 120, the artifact detectionunit 131 and the filter unit 151 in FIG. 1. The buffer unit 520 mayreceive and store a current image frame, and provide at least oneprevious image frame to the artifact detection unit 531 of the weightgeneration unit 530. On the other hand, the buffer unit 520 may receiveand store a color or brightness weight W corresponding to the currentimage frame generated by the artifact detection unit 531, and provide acolor or brightness weight W′ corresponding the previous image frame tothe artifact detection unit 531. The artifact detection unit 531 of theweight generation unit 530 is coupled to the buffer unit 520 to receivethe previous image frame and the color or brightness weight W′ thereof.

FIG. 6 is a flowchart illustrating an artifact reduction methodaccording to yet another embodiment of the invention. Referring to FIG.5 and FIG. 6, in step S610, the artifact detection unit 531 of theweight generation unit 530 reads one of a pixel in at least one previousimage frame (e.g., the pixel with coordinates i,j in a (k−1)^(th) imageframe) and the color or brightness weight W′ (e.g., a color weightWC′_(i,j) or a brightness weight WY′_(i,j)) corresponding to said pixel.In step S620, the artifact detection unit 531 of the weight generationunit 530 performs an artifact detection to pixel data of said pixel inthe current image frame (e.g., the pixel P_(i,j) with coordinates i,j ina k^(th) image frame) to obtain a detection result. For example, in stepS620, the artifact detection unit 531 may perform the artifact detectionin accordance with a relation of pixel data of said pixel in the currentimage frame and pixel data of said pixel in at least one previous imageframe.

An implementation of step S620 is not particularly limited herein. Insome embodiments, step S620 may include: comparing the color orbrightness value of said pixel in the current image frame with the coloror brightness value of said pixel in the at least one previous imageframe by the artifact detection unit 531, and a comparison resultthereof is used as the detection result for the artifact detection.

In step S630, the artifact detection unit 531 decides whether adjust thecolor or brightness weight W′ (e.g., the color weight WC′_(i,j) or thebrightness weight WY′_(i,j)) corresponding to said pixel in the previousimage frame. An implementation of step S630 is not particularly limitedherein. In some embodiments, step S630 may include: based on thecomparison result, deciding whether to adjust the color or brightnessweight W′ corresponding to said pixel in a plurality of weights of theat least one previous image frame (e.g., the color weight WC′_(i,j) orthe brightness weight WY′_(i,j) corresponding to the pixel P_(i,j) inthe (k−1)^(th) image frame), so as to generate the color or brightnessweight W corresponding to said pixel in the weights of the current imageframe (e.g., a color weight WC_(i,j) or a brightness weight WY_(i,j)corresponding to the pixel P_(i,j) in the k^(th) image frame).

In some embodiments, step S630 may include: if the comparison resultsatisfy a predetermined condition, adjusting the color or brightnessweight W′ corresponding to the pixel in the weights of the at least oneprevious image frame (e.g., the color weight WC′_(i,j) and/or thebrightness weight WY′_(i,j) corresponding to the pixel P_(i,j) in the(k−1)^(th) image frame) to be served as the color or bright weight Wcorresponding to said pixel in the weights of the current image frame(e.g., the color weight WC_(i,j) and/or the brightness weight WY_(i,j)corresponding to the pixel P_(i,j) in the k^(th) image frame); and ifthe comparison result does not satisfy the predetermined condition,resetting the color or brightness weight W corresponding to the pixel inthe current image frame.

Take NTSC system as an example, referring to FIG. 3 and FIG. 5, theartifact detection unit 531 may compare/analyze a relation between thethree of a pixel in the current image frame (e.g., the pixel P_(i,j)with coordinates i,j in the k^(th) image frame 330), the same pixel inthe second previous image frame (e.g., the pixel P_(i,j) withcoordinates i,j in the (k−2)^(th) image frame 320) and the same pixel inthe fourth previous image frame (e.g., the pixel P_(i,j) withcoordinates i,j in the (k−4)^(th) image frame 310) provided by thebuffer unit 520. For instance, if the relation between the three of thepixels P_(i,j) in the (k−4)^(th) image frame 310, the (k−2)^(th) imageframe 320 and the k^(th) image frame 330 satisfies a sinusoid (as shownin FIG. 3), the artifact detection unit 531 may determine that thecomparison result satisfies the predetermined condition.

Assuming that the pixels P_(i,j) in the image frames 310, 320 and 330include a brightness value Y, the artifact detection unit 531 may checkwhether the comparison result of the brightness value Y of the pixelsP_(i,j) in the image frames 310, 320 and 330 satisfies the predeterminedcondition (as shown in FIG. 3). Once the comparison result satisfies thepredetermined condition, it indicates that cross-luma occurs at thepixel P_(i,j) in the current image frame (e.g., the k^(th) image frame330). Therefore, when the comparison result satisfies the predeterminedcondition, the artifact detection unit 531 may perform calculation ofWY_(i,j)=WY′_(i,j)+inc, wherein WY_(i,j) is a brightness weightcorresponding to the pixel P_(i,j) in the current image frame (e.g., thek^(th) image frame 330), WY′_(i,j) is a brightness value correspondingto the pixel P_(i,j) in the previous image frame, (e.g., the (k−2)^(th)image frame 320), and inc is any real number greater than 0. In otherembodiments, inc may be a real number greater than 0 and less than 1, sothat the adjusted brightness weight WY_(i,j) may be less than or equalto 1. The brightness value WY_(i,j) may be used as a brightnesscomponent of the weights W, and the brightness weight WY′_(i,j) may beused as a brightness component of the weights W′. Otherwise, if thecomparison result does not satisfy the predetermined condition, theartifact detection unit 531 may perform calculation of WY_(i,j)=ini,wherein ini is an initial value (e.g., 0 or other real numbers).

Assuming that the pixels P_(i,j) in the image frames 310, 320 and 330include a color value C, the artifact detection unit 531 may checkwhether the comparison result of the color value C of the pixels P_(i,j)in the image frames 310, 320 and 330 satisfies the predeterminedcondition (as shown in FIG. 3). Once the comparison result satisfies thepredetermined condition, it indicates that cross-color occurs at thepixel P_(i,j) in the current image frame (e.g., the k^(th) image frame330). Therefore, when the comparison result satisfies the predeterminedcondition, the artifact detection unit 531 may perform calculation ofWC_(i,j)=WC′_(i,j)+inc, wherein WC_(i,j) is a color weight correspondingto the pixel P_(i,j) in the current image frame (e.g., the k^(th) imageframe 330), WC′_(i,j) is a color value corresponding to the pixelP_(i,j) in the previous image frame, (e.g., the (k−2)^(th) image frame320), and inc is any real number greater than 0. In other embodiments,inc may be a real number greater than 0 and less than 1, so that theadjusted color weight WC_(i,j) may be less than or equal to 1. The colorvalue WC_(i,j) may be used as a color component of the weights W, andthe color weight WC′_(i,j) may be used as a color component of theweights W′. Otherwise, if the comparison result does not satisfy thepredetermined condition, the artifact detection unit 531 may performcalculation of WC_(i,j)=ini, wherein ini is an initial value (e.g., 0 orother real numbers).

In step S640, the artifact detection unit 531 may use the adjusted coloror brightness weight as a color or brightness weight W corresponding tosaid pixel in the current image frame (e.g., the color weight WC_(i,j)or the brightness weight WY_(i,j) corresponding to the pixel P_(i,j) inthe k^(th) image frame) to be updated to the buffer unit 520. The filterunit 551 is coupled to the artifact detection unit 531. By using theadjusted color or brightness weight W provided by the artifact detectionunit 531, in step S640, the filter unit 551 of the adjusting unit 550may perform an image processing procedure to the current image frame toobtain the adjusted image frame. For instance, the filter unit 551 mayperform a temporal noise reduction (TNR) to the current image frame byusing the weights W for reducing artifact of the current image frame andobtaining the adjusted image frame.

Therefore, the artifact detection unit 531 may detect whether thecurrent image frame includes artifacts, and output the weights W to thefilter unit 551. The weights W are in response to the result of theartifact detection performed by the artifact detection unit 531 to thecurrent image frame. The filter unit 551 of the adjusting unit 550 mayreduce artifact of the current frame according to the weights W toobtain the adjusted image frame. Because the weight W′ corresponding tothe previous image frame may be reserved and superimposed, artifact maybe effectively reduced.

FIG. 7 is a block diagram illustrating circuitry of an artifactreduction apparatus 700 according to another embodiment of theinvention. The artifact reduction apparatus 700 includes a buffer unit520, an artifact detection unit 531, and an adjusting unit 551. Thebuffer unit 520 and the artifact detection unit 531 of FIG. 7 may beinferred by reference with related description of FIG. 5. The artifactdetection unit 531 and the filter unit 750 receive a current imageframe. The filter unit 750 may perform an image processing procedure tothe current image frame for reducing artifact of the current imageframe, and obtaining and outputting the adjusted image frame.

In the embodiment depicted in FIG. 7, the filter unit 750 includes aframe memory 751 and a temporal noise reduction (TNR) circuit 752. Theframe memory 751 may temporally store the adjusted image frame outputtedby temporal noise reduction circuit 752, and provide a previous adjustedimage frame to the temporal noise reduction circuit 752. The temporalnoise reduction circuit 752 is coupled to the frame memory 751 and theartifact detection unit 531. The temporal noise reduction circuit 752may perform a temporal noise reduction (TNR) to the current image frameaccording to the color or brightness weight W provided by the artifactdetection unit 531 and the previous adjusted image frame provided by theframe memory 751 for reducing artifact of the original image frame andobtaining the adjusted image frame.

For instance, for each pixel in the pixels of the current image frame,the temporal noise reduction circuit 752 of the filter unit 750 mayrespectively execute following steps: calculating an equation beingOut(f)=In(f)*(1−a)+In(f−1)*a. Therein, Out(f) indicates a color orbrightness value of a pixel of the adjusted image frame (e.g., the pixelP_(i,j) with coordinates i,j in a f^(th) adjusted image frame), In(f)indicates a color or brightness value of the pixel of the current imageframe (e.g., the pixel P_(i,j) with coordinates i,j in a f^(th) originalimage frame), In(f−1) indicates a color or brightness value of the pixelof the previous adjusted image frame (e.g., the pixel P_(i,j) withcoordinates i,j in a (f−1)^(th) adjusted image frame) provided by theframe memory 751, and a indicates a color or brightness weight Wcorresponding to the pixel (e.g., the pixel P_(i,j)) in the weights.

In summary, because the artifact detection unit according to theembodiments of the invention is capable of reserving and superimposingthe weights corresponding to the previous image frame to be used as theweights corresponding to the current image frame, artifact of thecurrent image frame may be effectively and rapidly reduced to obtain theadjusted image frame. In addition, according to some other embodiments,because the artifact reduction apparatus and method are capable ofscaling down the resolution of the original image for the artifactdetection, the circuit area and the calculation complexity of theartifact detection unit may be saved, and the memory space of the bufferunit may also be saved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentdisclosure without departing from the scope or spirit of the disclosure.In view of the foregoing, it is intended that the present disclosurecover modifications and variations of this disclosure provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. An artifact reduction method, comprising: scalingdown a resolution of each of at least one previous original image framefrom a first resolution to a second resolution to obtain at least oneprevious low-resolution image frame and storing the at least oneprevious low-resolution image frame in a buffer unit; scaling down aresolution of a current original image frame from the first resolutionto the second resolution to obtain a current low-resolution image frame,wherein the current original image frame and the current low-resolutionimage frame comprise a first plurality of pixels and a second pluralityof pixels, respectively; performing an artifact detection to the currentlow-resolution image frame to obtain a plurality of low-resolutionweights in accordance with a relation of the current low-resolutionimage frame and the at least one previous low-resolution image frameretrieved from the buffer unit, wherein the low-resolution weights arerespectively corresponding to the second plurality of pixels in thecurrent low-resolution image frame, and the step of performing theartifact detection to the current low-resolution image frame to obtainthe low-resolution weights comprises: for each pixel in the secondplurality of pixels of the current low-resolution image frame,respectively executing following steps: (i) comparing a color orbrightness value of a pixel in the current low-resolution image framewith a color or brightness value of the pixel in the at least oneprevious low-resolution image frame; and (ii) if the comparison resultsatisfies a predetermined condition, adjusting a color or brightnessweight corresponding to the pixel in the low-resolution weights of theat least one previous low-resolution image frame to generate the coloror brightness weight corresponding to the pixel in the low-resolutionweights of the current low-resolution image frame; scaling up a numberof the low-resolution weights to generate a plurality of high-resolutionweights, wherein the high-resolution weights are respectivelycorresponding to the first plurality of pixels in the current originalimage frame; and performing a temporal noise reduction to the currentoriginal image frame by using the high-resolution weights for reducingartifact of the current original image frame and obtaining an adjustedimage frame, wherein the step of performing the temporal noise reductionto the current original image frame comprises: for each pixel in thefirst plurality of pixels of the current original image frame,respectively executing following steps: calculating a color orbrightness value of a pixel in an adjusted image frame based on a coloror brightness value of the pixel in the current original image frame, acolor or brightness value of the pixel in a previous adjusted imageframe, and a color or brightness weight corresponding to the pixel inthe high-resolution weights.
 2. The artifact reduction method of claim1, wherein if the comparison result does not satisfy the predeterminedcondition, resetting the color or brightness weight corresponding to thepixel in the current low-resolution image frame.
 3. The artifactreduction method of claim 1, wherein the step of performing the temporalnoise reduction to the current original image frame further comprises:for each pixel in the first plurality of pixels of the current originalimage frame, respectively executing following steps: calculating anequation being Out(f)=In(f)*(1−a)+In(f−1)*a, wherein Out(f) indicatesthe color or brightness value of the pixel in the adjusted image frame,In(f) indicates the color or brightness value of the pixel in thecurrent original image frame, In(f−1) indicates the color or brightnessvalue of the pixel in the previous adjusted image frame, and a indicatesthe color or brightness weight corresponding to the pixel in thehigh-resolution weights.
 4. An image processing method, comprising:scaling down a resolution of each of at least one previous originalimage frame from a first resolution to a second resolution to obtain atleast one previous low-resolution image frame and storing the at leastone previous low-resolution image frame in a buffer unit; scaling down aresolution of a current original image frame from the first resolutionto the second resolution to obtain a current low-resolution image frame,wherein the current original image frame and the current low-resolutionimage frame comprise a first plurality of pixels and a second pluralityof pixels, respectively; generating a plurality of low-resolutionweights according to a relation of the current low-resolution imageframe and the at least one previous low-resolution image frame retrievedfrom the buffer unit, wherein the low-resolution weights arerespectively corresponding to the second plurality of pixels of thecurrent low-resolution image frame, and the step of generating thelow-resolution weights comprises: for each pixel in the second pluralityof pixels of the current low-resolution image frame, respectivelyexecuting following steps: (i) comparing a color or brightness value ofa pixel in the current low-resolution image frame with a color orbrightness value of the pixel in the at least one previouslow-resolution image frame; and (ii) if the comparison result satisfiesa predetermined condition, adjusting a color or brightness weightcorresponding to the pixel in the low-resolution weights of the at leastone previous low-resolution image frame to generate the color orbrightness weight corresponding to the pixel in the low-resolutionweights of the current low-resolution image frame; scaling up a numberof the low-resolution weights to generate a plurality of high-resolutionweights, wherein the high-resolution weights are respectivelycorresponding to the first plurality of pixels of the current originalimage frame; and performing an image processing procedure to the currentoriginal image frame by using the high-resolution weights to obtain anadjusted image frame, wherein the step of performing the imageprocessing procedure to the current original image frame comprises: foreach pixel in the first plurality of pixels of the current originalimage frame, respectively executing following steps: calculating a coloror brightness value of a pixel in an adjusted image frame based on acolor or brightness value of the pixel in the current original imageframe, a color or brightness value of the pixel in a previous adjustedimage frame, and a color or brightness weight corresponding to the pixelin the high-resolution weights.
 5. An artifact reduction apparatus,comprising: a scaling-down circuitry scaling down a resolution of eachof at least one previous original image frame from a first resolution toa second resolution to obtain at least one previous low-resolution imageframe, and scaling down a resolution of a current original image framefrom the first resolution to the second resolution to obtain and outputa current low-resolution image frame, wherein the current original imageframe and the current low-resolution image frame comprise a firstplurality of pixels and a second plurality of pixels, respectively; abuffer unit, coupled to the scaling-down circuitry, receiving andstoring the at least one previous low-resolution image frame and thecurrent low-resolution image frame; an artifact detection circuitrycoupled to the scaling-down circuitry and the buffer unit, wherein theartifact detection circuitry performs an artifact detection to thecurrent low-resolution image frame to obtain and output a plurality oflow-resolution weights in accordance with a relation of the currentlow-resolution image frame provided by the scaling-down circuitry andthe at least one previous low-resolution image frame provided by thebuffer unit, wherein the low-resolution weights are respectivelycorresponding to the second plurality of pixels in the currentlow-resolution image frame, and for each pixel in the second pluralityof pixels of the current low-resolution image frame, the artifactdetection circuitry respectively executes following steps: (i) comparinga color or brightness value of a pixel in the current low-resolutionimage frame with a color or brightness value of the pixel in the atleast one previous low-resolution image frame (ii) if the comparisonresult satisfies a predetermined condition, adjusting a color orbrightness weight corresponding to the pixel in the low-resolutionweights of the at least one previous low-resolution image frame togenerate the color or brightness weight corresponding to the pixel inthe low-resolution weights of the current low-resolution image frame; ascaling-up circuitry coupled to the artifact detection circuitry,wherein the scaling-up circuitry scales up a number of thelow-resolution weights to obtain and output a plurality ofhigh-resolution weights, wherein the high-resolution weights arerespectively corresponding to the first plurality of pixels in thecurrent original image frame; and a filter circuitry coupled to thescaling-up circuitry, wherein the filter circuitry performs an imageprocessing procedure to the current original image frame by using thehigh-resolution weights for reducing artifact of the current originalimage frame and obtaining an adjusted image frame, wherein for eachpixel in the first plurality of pixels of the current original imageframe, the filter circuitry respectively executes following steps:calculating a color or brightness value of a pixel in an adjusted imageframe based on a color or brightness value of the pixel in the currentoriginal image frame, a color or brightness value of the pixel in aprevious adjusted image frame, and a color or brightness weightcorresponding to the pixel in the high-resolution weights.
 6. Theartifact reduction apparatus of claim 5, wherein if the comparisonresult does not satisfy the predetermined condition, resetting the coloror brightness weight corresponding to the pixel in the currentlow-resolution image frame.
 7. The artifact reduction apparatus of claim5, wherein for each pixel in the first plurality of pixels of thecurrent original image frame, the filter circuitry respectively executesfollowing steps: calculating an equation beingOut(f)=In(f)*(1−a)+In(f−1)*a, wherein Out(f) indicates the color orbrightness value of the pixel in the adjusted image frame, In(f)indicates the color or brightness value of the pixel in the currentoriginal image frame, In(f−1) indicates the color or brightness value ofthe pixel in the previous adjusted image frame, and a indicates thecolor or brightness weight corresponding to the pixel in thehigh-resolution weights.
 8. The artifact reduction apparatus of claim 5,wherein the filter circuitry comprises: a frame memory configured tostore the adjusted image frame and provide a previous adjusted imageframe; and a temporal noise reduction circuit coupled to the framememory, and configured to perform a temporal noise reduction to thecurrent original image frame according to the high-resolution weightsand the previous adjusted image frame for reducing artifact of thecurrent original image frame and obtaining the adjusted image frame. 9.An image processing apparatus, comprising: a scaling-down circuitryscaling down a resolution of each of at least one previous originalimage frame from a first resolution to a second resolution to obtain atleast one previous low-resolution image frame, and scaling down aresolution of a current original image frame from the first resolutionto the second resolution to obtain a current low-resolution image frame,wherein the current original image frame and the current low-resolutionimage frame comprise a first plurality of pixels and a second pluralityof pixels, respectively; a buffer unit, coupled to the scaling-downcircuitry, receiving and storing the at lest one previous low-resolutionimage frame and the current low-resolution image frame; a weightgeneration circuitry, coupled to the scaling-down circuitry and thebuffer unit, generating a plurality of low-resolution weights accordingto a relation of the current low-resolution image frame provided by thescaling-down circuitry and the previous low-resolution image frameprovided by the buffer unit, wherein the low-resolution weights arerespectively corresponding to the second plurality of pixels in thecurrent low-resolution image frame, and for each pixel in the secondplurality of pixels of the current low-resolution image frame, theweight generation circuitry respectively executes following steps: (i)comparing a color or brightness value of a pixel in the currentlow-resolution image frame with a color or brightness value of the pixelin the at least one previous low-resolution image frame (ii) if thecomparison result satisfies a predetermined condition, adjusting a coloror brightness weight corresponding to the pixel in the low-resolutionweights of the at least one previous low-resolution image frame togenerate the color or brightness weight corresponding to the pixel inthe low-resolution weights of the current low-resolution image frame; ascaling-up circuitry scaling up a number of the low-resolution weightsto generate a plurality of high-resolution weights, wherein thehigh-resolution weights are respectively corresponding to the firstplurality of pixels in the current original image frame; and anadjusting circuitry performing an image processing procedure to thecurrent original image frame by using the high-resolution weights toobtain an adjusted image frame, wherein for each pixel in the firstplurality of pixels of the current original image frame, the adjustingcircuitry respectively executes following steps: calculating a color orbrightness value of a pixel in an adjusted image frame based on a coloror brightness value of the pixel in the current original image frame, acolor or brightness value of the pixel in a previous adjusted imageframe, and a color or brightness weight corresponding to the pixel inthe high-resolution weights.